Line pans of unit length (1500 cm or 5 ft) are secured together, end-to-end in articulated manner to build up a conveyor to desired length e.g. 200 m, each pan comprising a pair of mutually facing, spaced-apart, elongate, sigma-section sidewalls, interconnected by a deck plate welded to both sidewalls to separate an upper, conveying run, from a lower return run, with a plurality of transversely extending flight bars attached at regular intervals to at least one endless chain and with a drive sprocket barrel assembly provided at at least one end of the conveyor and a return sprocket barrel assembly provided at the other end of the conveyor.
Scraper chain conveyors are used extensively in mineral mining operations, particularly coal mining, by being located along a mineral face and serving not only to convey away mineral mined from the face, but also as a guide track for an associated mining machine adapted to be reciprocated to and fro along the conveyor. Machine reciprocation is by a haulage system comprising at least one machine mounted drive sprocket, powered from an onboard source, and, for the so-called "chainless" haulages developed over the last 20 years, adapted to engage a rack associated with the conveyor. Various rack arrangements are in operation but all have required the securing, by bolting and/or welding, of mounting and/or trapping furnishings to one of the conventional sigma-section sidewalls of a line pan. Inevitably, during mining operations, damage or deformation of the furnishings occur, requiring replacement. With a wholly bolted construction, or part bolted construction, the bolts are frequently difficult to release as a result of deformation and/or rusting from water sprays provided for dust supression etc. With a wholly welded construction, or part welded construction, weld fatigue occurs due to stresses, vibrations, overloading etc., in practice, while frequently compromises must be made in the steel specification from an optimum specification to one with improved weldability, while furthermore the entire pan (conventionally 1500 cm length) must be withdrawn from the conveyor for surface repair (under British regulations) or underground repair at a safe area (under U.S. regulations).
Apart from the interruption to mineral production, the furnishings are usually outboard of the conveyor width, (c.f. GB 2,176,522, GB 2,196,366, GB 2,094,866, GB 2,058,882, GB 2,054,702, GB 1,534,029, GB 1,528,398), which may result in the taking of a reduced web of mineral during each traverse. Also, the machine must be captivated to the conveyor by slide shoes engaging a captivating flange whilst the machine must also carry a scraper to scrape fines from the top surface of the sidewall of each pan to prevent the captivating path being obstructed by fines.